New guidelines issued by the UK General Medical Council (GMC) will allow doctors to disclose genetic information to relatives - even when patients object, if there are compelling medical reasons for doing so. The guidance, which comes into effect on 12 October, acknowledges that confidentiality is not always absolute; disclosing information about a genetic link to a disease may protect another individual from serious harm. For example, if a patient is diagnosed with a hereditary form of cancer, a doctor will now be able to inform relatives about the potential risk the genetic link could carry. Awareness of such a genetic risk could prompt investigation for the genetic mutation responsible and regular screening, thereby improving the chance of early detection and long-term prognosis.